This invention relates generally to tomosynthesis and more particularly to a method and apparatus for acquiring a plurality of images using a tomosynthesis imaging system using a reduced compression force.
In at least some known imaging systems, a radiation source projects a cone-shaped beam which passes through the object being imaged, such as a patient and impinges upon a rectangular array of radiation detectors. In some known tomosynthesis systems, the radiation source rotates with a gantry around a pivot point, and views of the object are acquired for different projection angles. As used herein xe2x80x9cviewxe2x80x9d refers to a single projection image or, more particularly, xe2x80x9cviewxe2x80x9d refers to a single projection radiograph which forms a projection image. Also, as used herein, a single reconstructed (cross-sectional) image, representative of the structures within the imaged object at a fixed height above the detector, is referred to as a xe2x80x9cslicexe2x80x9d. And a collection (or plurality) of views is referred to as a xe2x80x9cprojection dataset.xe2x80x9d A collection of (or a plurality of) slices for all heights is referred to as a xe2x80x9cthree-dimensional dataset representative of the image object.xe2x80x9d
One known method of reconstructing a three-dimensional dataset representative of the imaged object is known in the art as simple backprojection, or shift-and-add. Simple backprojection backprojects each view across the imaged volume, and averages the backprojected views. A xe2x80x9cslicexe2x80x9d of the reconstructed dataset includes the average of the backprojected images for some considered height above the detector. Each slice is representative of the structures of the imaged object at the considered height, and the collection of these slices for different heights, constitutes a three-dimensional dataset representative of the imaged object.
In some known imaging systems, a compression force is applied to a breast to improve image quality by reducing a thickness of the breast thereby spreading the breast tissue over a larger area. The reduction in the breast thickness, and spreading the breast over a larger area, facilitate interpretation of the projection radiographs, because the amount of xe2x80x9coverlying tissuexe2x80x9d for structures within the imaged breast is minimized in the projection radiograph. Reduction of the breast thickness by compression is also important in managing a patient radiation dosage. In general, the thicker the compressed breast, the more x-ray attenuation. Therefore, a higher dosage is applied to a thicker breast to keep an x-ray signal level at the detector essentially constant. This is particularly important in a film/screen system, where the film is not appropriately xe2x80x9cblackenedxe2x80x9d if the radiation dosage is either too high or too low. Some known patients may experience discomfort due to the compression force applied to the breast and may not schedule any future examinations, thereby possibly increasing the patient""s risk that a serious medical condition may not be detected in a timely fashion.
In one embodiment, a method for acquiring a plurality of images of an object of interest using a tomosynthesis imaging system is provided. The method includes determining a thickness of an object of interest, and adjusting at least one parameter of an image acquisition process based on the determined thickness.
In another embodiment, a method for operating a tomosynthesis imaging system is provided. The method includes providing an object of interest and generating a mammographic compressed thickness of the object. The method also includes adjusting the mammographic compressed thickness by adding one-half centimeter to the mammographic compressed thickness when the mammographic compressed thickness is less than four and one-half centimeters thick and adding one centimeter to the mammographic compressed thickness when the mammographic compressed thickness is at least four and one-half centimeters thick, and using the adjusted mammographic compressed thickness to perform a tomosynthesis scan.
In a further embodiment, a tomosynthesis imaging system for acquiring a plurality of images of an object of interest is provided. The tomosynthesis imaging system includes a detector array, at least one radiation source, a compression force indicator, a compressed breast thickness indicator, and a computer coupled to the detector array and the radiation source. The computer is configured to determine a thickness of an object of interest and adjust at least one parameter of an image acquisition process based on the determined thickness.
In a still further embodiment, a computer readable medium encoded with a program executable by a computer for controlling an imaging system is provided. The imaging system includes a radiation source and a digital detector. The program is configured to instruct the computer to determine a thickness of an object of interest and adjust at least one parameter of an image acquisition process based on the determined thickness.